When NASA began thinking about missions to look for life beyond Earth, it realized it had a problem: how to recognize life if it were found.

Scientists came up with a definition for life — a self-sustaining chemical system capable of Darwinian evolution — but remained understandably fuzzy on the details.

It is still not known how life on Earth took hold, what happened to a bunch of chemicals that made them capable of supporting a metabolism, replicating and evolution. But a new field of science, called synthetic biology, is aiming to find out.

One of the most promising developments lies in a beaker of water inside a Florida laboratory. It's an experiment called AEGIS — an acronym for Artificially Expanded Genetic Information System. Its creator, Steve Benner, says it is the first synthetic genetic system capable of Darwinian evolution.

AEGIS is not self-sustaining, at least not yet, and with 12 DNA building blocks — as opposed to the usual four — there's little chance it will be confused with natural life. Still, Benner is encouraged by the results.

"It's evolving. It's doing what we designed it to do," said Benner, a biochemist with the Gainesville, Fla.-based Foundation for Applied Molecular Evolution.

In addition to providing an example of how alien life might be cobbled together, synthetic biology has a broad array of uses on the home front.

Scientists at the University of California at Berkeley, for example, have created an organism to produce artemisinic acid, which is used as a malaria medication. It is normally extracted from the Artemisia annua plant. The synthetic variety is expected to be less expensive to produce.

"The underlying goal of synthetic biology is to make biology easy to engineer," said Drew Endy, a bioengineer with the Massachusetts Institute of Technology.

"When I want to go build some new biotechnology, whether it makes a food that I can eat or a bio-fuel that I can use in my vehicle, or I have some disease I want to try and cure, I don't want that project to be a research project. I want it to be an engineering project," he said.